High response compact turbocharger

ABSTRACT

Turbochargers of this invention comprise a turbine housing and a turbine wheel rotatably disposed therein. A center housing is connected to the turbine housing, and a compressor housing is attached to the center housing. A compressor is rotatably disposed within the compressor housing, and comprises two impellers placed in back-to-back orientation. A movable member is disposed within the compressor housing to downstream of the compressor to control the flow of air within the compressor housing. The position of the movable member can be operated to control the amount of pressurized air that is produced by one of the compressor impellers to provide enhanced compressor operating efficiency throughout the operating range and mass flow requirements of the engine.

FIELD OF THE INVENTION

This invention relates to turbochargers and, more specifically, toturbochargers comprising a dual compressor construction that arespecially configured to provide a desired level of high efficiency, highresponse and provide a compact turbocharger package when compared toconventional single compressor turbochargers.

BACKGROUND OF THE INVENTION

As turbocharged diesel engines have developed to higher brake meaneffective pressure (BMEP) levels, with low levels of legislatedemissions, it has become increasingly difficult to match the turbine andcompressor in conventional single compressor and/or single turbineturbochargers, and achieve the desired level of performance. Emissionsregulations enacted but not yet in force, may force extreme levels ofExhaust Gas Recirculation to control NOx and Particulate Filters tocontrol soot and particulate emissions. Generally, the compressor mustprovide the level of mass flow that the engine requires at its maximumpower, and this requirement operates to set the size of the compressor.In general, the compressor inducer throat area, i.e., the portion of thecompressor that meets incoming air and that is characterized by designparameters that include the inducer diameter, blade inlet angle, andblade blockage, determines the compressor flow. The boost pressureneeded to achieve a given level of mass flow is a function of the enginedesign and flow characteristics. The speed of the compressor isdetermined by its diameter and impeller blade backward curvature. Theturbine must produce the power necessary to drive the compressor at thespeed demanded by the compressor to reach the boost pressure and massflow required by the engine. Thus there is always a compromise toachieve the turbine match.

Radial turbines operate best when the turbine blade tip speed divided bythe isentropic spouting velocity (commonly referred to as U/Co) isapproximately 0.7. Unfortunately, several design features of futureengines make this difficult to achieve. The maximum corrected flow ofthe turbine is a function of its size and blade curvature. Ultra-highboost pressures reduce the required maximum turbine corrected flow, asdoes the inclusion of exhaust gas recirculation (EGR). EGR essentiallyreduces the fresh air volumetric efficiency of the engine, thusrequiring higher boost pressures to pass the required fresh air. This inturn requires more turbine power which is achieved by increasing thebackpressure on the engine.

Other devices that increase the backpressure on the turbine such asdiesel particulate filters, all types of catalysts, or turbo-compoundturbines also operate to reduce the required turbine corrected flow. Asthe pressure at which the turbine discharges to is raised, and thepressure ratio of the turbine is held constant to produce the requiredpower, the inlet pressure of the turbine is significantly increased.This increase in turbine inlet pressure results in higher densityexhaust gas, and thus lower corrected flow. As the power densities haveincreased and the aforementioned devices have become more and morecommon, the challenge to correctly match the turbine and compressor hasincreased.

Achieving good low engine speed performance requires that the turbineflow be reduced to generate good boost pressures with the minimumexhaust energy that is available. This has given rise to the use ofvariable geometry turbines. In such variable geometry turbines theturbine geometry is configured to be controlled to reduce the flow areaof the turbine and generate more backpressure. This higher backpressureresults in an increased expansion ratio for the turbine, which functionsto create more turbine power.

When taken to extremes, such as that seen when accelerating the enginerapidly from idle, the turbine performance is quite poor. There areseveral causes for this. First, the wheel and turbine nozzle areoperating at far off design, and the U/Co is not in the optimumoperating zone. Second, the turbine flow area is substantially closedresulting in a high-pressure loss through the flow control device (suchas an adjustable vaned nozzle cascade).

Conventional turbochargers would have to be configured having a largecompressor with a very small turbine due to the aforementioned reasons.To counteract this, it is possible to use a high trim (large inducersize) compressor, with high backward curvature to increase theturbocharger speed to improve the turbine match. The turbine can also beconfigured having a low trim turbine to match the flow characteristicand force the diameter of the turbine as large as possible. However,these design alternatives may not be desirable from other points of viewsuch as fatigue life, packaging, efficiency, inertia, etc.

In conclusion, the future highly rated, low emission turbo-diesel enginewill require a fundamentally different concept of turbocharger designthan is presently provided by conventional turbochargers comprising asingle radial compressor driven by a single radial turbine.

To overcome the above-noted deficiency, different approaches have beentaken that each involve using two turbochargers. The three most populartwo- turbocharger configurations are commonly referred to as series,parallel/sequential, or staged. The common theme of all three conceptsis that a small turbocharger (roughly half the size or smaller than anormal full range single turbocharger) is used at the low end of thespeed range for best performance.

Enhanced transient performance is achieved by the initial use of asmaller turbocharger due to a number of reasons. First, the compressoris not operating near the surge line where efficiency is poor, butcloser to the peak efficiency island. Second, the turbine is also muchsmaller and better matched for the low flows. This is true whether fixedgeometry, wastegated and variable geometry turbines are used. For fixedgeometry and wastegated turbines, the turbine housing A/r (whichcontrols the flow characteristic) is closer to the optimum forefficiency. With a variable geometry turbine, the turbine size isreduced, and the nozzle setting becomes more open and reduces the flowloss through the vane cascade. Third, a smaller turbocharger has lessrotating group inertia, thus less turbine power is consumed increasingthe speed of the turbocharger and is applied to the compressor togenerate boost pressure.

A second turbocharger matching problem is known to exist with atraditional single turbo approach, separate and apart from the turbinematching issues discussed above for these new engines. The improvedengine responsiveness at low speed, combined with high power levels atfull speed, has resulted in a compressor range problem. Utilizingstate-of-the-art aerodynamic analysis to increase the flow range of thecompressor has yielded impressive improvements. However they still fallshort of engine manufacturer's expectations. The compressor surge line(a parameter in defining the compressor flow range) limits many engines'low speed torque.

This flow range issue has resulted in development work on variablegeometry compressors as well as the use of two turbochargers asmentioned previously. While variable geometry compressors can improvethe performance of the compressor, they add more complexity, movingparts, cost, and control elements to the engine. While multipleturbochargers in either staged, series, or parallel/sequentialarrangement, can help improve engine performance at the low end of thespeed range and have improved compressor range, they also add cost,complexity, weight, and packaging challenges to the engine.

It is, therefore, desirable that a turbocharger be constructed in amanner to provide a degree of turbocharger matching that enables theengine to produce the desired BMEP level and meet legislated emissionslimits. It is desired that such a turbocharger be constructed in amatter that can permit retrofit or new application use with a minimum ofancillary modifications. It is further desired that such a turbochargerbe constructed in a manner that is space efficient to promote efficientengine compartment packaging.

SUMMARY OF THE INVENTION

Turbocharger assemblies of this invention comprise a turbine housing,and a turbine wheel that is rotatably disposed within the turbinehousing. The turbine housing is attached to one end of a shaft. Theturbocharger includes a center housing that is connected to one end ofthe turbine housing, and is configured to carry the shaft therein. Acompressor housing is attached to a portion of the center housingopposite from the turbine housing.

Turbochargers of this invention comprise a compressor that is rotatablydisposed within the compressor housing. The compressor is attached tothe shaft and comprises two impellers that are placed in back-to-backorientation with one another. The compressor can comprise impellers thatare integral or separate from one another. The compressor housingincludes at least one air inlet for directing inlet air into thecompressor housing and to the compressor impellers.

The turbocharger further comprises means for controlling the flow of airwithin the compressor housing. In an example embodiment, such means isin the form of a movable member that is positioned downstream from thecompressor and that is configured to block the passage of pressurizedair produced by one of the compressor impellers when actuated. In apreferred embodiment, the movable member is annular and is disposedwithin a compressor housing wall cavity and is designed to project fromthe cavity a desired amount to impair the passage of pressurized air.The movable member is used to regulate the amount of pressurized airexiting the compressor housing for the purpose of providing enhancedcompressor operating efficiency throughout the operating range and massflow requirements of the engine.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more clearly understood with reference to thefollowing drawings wherein:

FIG. 1 illustrates a schematic diagram of an embodiment of aturbocharger constructed according to principles of this invention asused within an internal combustion engine;

FIG. 2 illustrates a schematic diagram of another embodiment of aturbocharger constructed according to principles of this invention asused within an internal combustion engine;

FIG. 3 illustrates a schematic diagram of another embodiment of aturbocharger constructed according to principles of this invention asused within an internal combustion engine;

FIG. 4 illustrates a schematic diagram of another embodiment of aturbocharger constructed according to principles of this invention asused within an internal combustion engine;

FIG. 5 illustrates a schematic diagram of another embodiment of aturbocharger constructed according to principles of this invention asused within an internal combustion engine;

FIG. 6 illustrates a schematic diagram of another embodiment of aturbocharger constructed according to principles of this invention asused within an internal combustion engine;

FIG. 7 illustrates a schematic diagram of another embodiment of aturbocharger constructed according to principles of this invention asused within an internal combustion engine;

FIG. 8 illustrates a schematic diagram of another embodiment of aturbocharger constructed according to principles of this invention asused within an internal combustion engine;

FIG. 9 illustrates a schematic side view of an embodiment of aturbocharger of this invention comprising separate axially positionedair inlets;

FIG. 10 illustrates a schematic side view of another embodiment of aturbocharger of this invention comprising separate axially positionedair inlets and an air flow control means;

FIG. 11 illustrates a schematic side view of another embodiment of aturbocharger of this invention comprising separate axially positionedair inlets, an air flow control means, and a actuation means;

FIG. 12 illustrates a schematic side view of another embodiment of aturbocharger of this invention comprising concentric axially positionedair inlets and an air flow control means;

FIG. 13 illustrates a cross-sectional side view of another embodiment ofa turbocharger of this invention having concentric axially positionedair inlets and air flow control means;

FIG. 14 illustrates a cross-sectional side view of another embodiment ofa turbocharger of this invention comprising a single radial air inlet;and

FIG. 15 illustrates a cross-sectional side view of another embodiment ofa turbocharger of this invention comprising having dual radial airinlets and air flow control means.

DETAILED DESCRIPTION

Turbochargers of this invention generally comprise dual compressorsarranged in a back-to-back configuration that are specifically designedto provide an improved degree of turbine matching to improve compressorand turbine efficiency, and to produce a desired air mass flow rate tothe engine while also meeting engine emission requirements. Theseturbochargers include a compressor housing and surrounding architecturethat is specifically constructed to accommodate the dual compressorstherein, and are designed to facilitate air inlet flow to bothcompressors in a manner that is ideally balanced. These turbochargersmay further include means for regulating the amount of pressurized airexiting the compressor housing for the purpose of providing an expandedcompressor operating envelope, and enhanced compressor operatingefficiency throughout the operating range and mass flow requirements ofthe engine.

FIG. 1 schematically illustrates a turbocharged internal combustionengine system 10 comprising an internal combustion engine 12, which canbe a gasoline or diesel engine, having an air intake manifold 14 and anexhaust gas manifold 16 attached thereto. A turbocharger 18 of thisinvention is mounted near the engine 12 and includes a turbine housingthat comprises a turbine wheel or turbine 20 disposed therein, that ismounted to a shaft 22 disposed within a center housing that is mountedto the turbine housing. The turbine wheel 20 receives exhaust gas fromthe engine via suitable connection means 24, connecting the exhaustmanifold to the turbine housing.

The turbocharger 18 comprises a compressor housing that is attached toan opposite axial end of the center housing, and that includes dualcompressor impellers or compressors 26 and 28 rotatably disposedtherein. The compressors are placed in a back-to-back orientation andare both connected to the shaft 22 for rotary activation by the turbine20. The compressor housing is specifically constructed having an airinlet 30 that is configured to direct air to each of the compressors 26and 28. As explained in greater detail below, the air inlet may beconfigured a variety of different ways depending on the particularapplication and design parameters/objectives. Also, as better explainedbelow, the compressors are specially sized and configured to provideimproved turbine matching, when compared to conventional singlecompressor turbochargers, to produce both an improved compressorefficiency and desired improvement in BMEP.

A cooler 32, e.g., an air-to-air charge cooler, can be used to reducethe temperature of pressurized air leaving the compressor housing, andis interposed between the compressor housing and the engine intakemanifold.

The particular system described and illustrated above is provided forthe purpose of referencing a turbocharger as constructed according tothis invention in its most elementary form. If desired, other devicescan be used with the turbocharger of this invention to achieve desiredchanges in turbocharger performance. For example, air or gas flowcontrolling means can be can be used in association with turbochargersof this invention to achieve control over the flow of air to or from theturbocharger. Such means can be part of the turbocharger itself, or canbe separate from the turbocharger. Also, it is understood thatturbochargers of this invention can be configured having one or morevariable geometry members used in association with the turbine, tocontrol the amount of exhaust gas being directed to the turbine wheel,or used in association with the compressor, to control the amount ofpressurized gas exiting the compressor housing.

FIG. 2 schematically illustrates a turbocharged internal combustionengine system 34 comprising the same general components noted above andillustrated in FIG. 1. In addition, this system 34 includes a flowcontrolling means 36 that is positioned upstream from one of thecompressors 26. Such flow controlling means can be positioned within oroutside of the compressor housing, and can be actuated by an enginecontroller or other means to control the amount of inlet air directed tothe compressor depending on the particular operating condition of theengine to control the onset of surge flow, thereby providing mostefficient compressor operation that meets the particular engine massflow requirements.

FIG. 3 schematically illustrates a turbocharged internal combustionengine system 38 comprising the same general components noted above andillustrated in FIG. 1. In addition, this system 38 includes a flowcontrolling means 40 that is positioned downstream from one of thecompressors 26. Such flow controlling means can be positioned within oroutside of the compressor housing, and can be actuated by an enginecontroller or other means to control the amount of inlet air directed tothe compressor depending on the particular operating condition of theengine to control the onset of surge flow, thereby providing mostefficient compressor operation that meets the particular engine massflow requirements.

FIG. 4 schematically illustrates a turbocharged internal combustionengine system 42 comprising the same general components noted above andillustrated in FIG. 1. In addition, this system 42 includes both theflow controlling means 36 illustrated in FIG. 2, that is positionedupstream from one of the compressors 26, and the flow controlling means40 illustrated in FIG. 3, that is positioned downstream from one of thecompressors 26. Again, these flow controlling means can be positionedwithin or outside of the compressor housing, and can be actuated by anengine controller or other means to control the amount of inlet airchanneled to the compressor depending on the particular operatingcondition of the engine to control the onset of surge flow, therebyproviding most efficient compressor operation that meets the particularengine mass flow requirements.

FIG. 5 schematically illustrates a turbocharged internal combustionengine system 44 comprising the same general components noted above andillustrated in FIG. 1. In addition, this system 44 includes a bypassflow path 46 between the compressor outlet and inlet, and a flowcontrolling means 48 that is positioned within the bypass flow path. Inthis particular embodiment, a portion of the pressurized air produced inthe compressor housing can be directed back to the compressor withoutcooling, e.g., is taken upstream of the cooler. The bypass flow path isprovided to permit the routing and combining of pressurized air exitingthe turbocharger with inlet air entering the compressor housing. Theflow controlling means 48 can be positioned within or outside of thecompressor housing, and can be actuated by an engine controller or othermeans to control the amount of pressurized air channeled to thecompressor depending on the particular operating condition of the engineto increase compressor flow range, thereby providing most efficientcompressor operation that meets the particular engine mass flowrequirements.

FIG. 6 schematically illustrates a turbocharged internal combustionengine system 50 comprising the same general components noted above andillustrated in FIG. 1. In addition, this system 50 includes bypass flowpath 52 between the charge cooler 32 and the compressor air inlet, and aflow controlling means 54 that is positioned within the bypass flowpath. In this particular embodiment, the pressurized air is directedback to the compressor after it is cooled, e.g., is taken downstream ofthe cooler 32. The bypass flow path is provided to permit the routingand combining of pressurized air exiting the turbocharger with inlet airentering the compressor housing. The flow controlling means 54 ispositioned outside of the compressor housing, and can be actuated by anengine controller or other means to control the amount of cooledpressurized air channeled to the compressor depending on the particularoperating condition of the engine to increase compressor flow range,thereby providing most efficient compressor operation that meets theparticular engine mass flow requirements.

FIG. 7 schematically illustrates a turbocharged internal combustionengine system 56 comprising the same general components noted above andillustrated in FIG. 1. In addition, this system 56 includes a flowcontrolling means 58 that is positioned upstream from the turbine wheel20. Such flow controlling means can be positioned within or outside ofthe turbine housing. For example, the flow controlling means 58 can bein the form of one or more variable geometry members that are positionedwithin the turbocharger such as those disclosed in U.S. Pat. No.6,269,642, which are each hereby incorporated herein by reference. Theflow controlling means can be actuated by an engine controller or othermeans to control the amount of exhaust gas directed to turbine wheeldepending on the particular operating condition of the engine. Together,the dual compressors and variable geometry turbine members operate toprovide efficient turbocharger operation that meets the particularengine mass flow requirements.

FIG. 8 schematically illustrates a turbocharged internal combustionengine system 60 comprising the same general components noted above andillustrated in FIGS. 1 and 8. In addition, this system 60 includes aflow controlling means 62 that is positioned downstream from thecompressors 26 and 28. Such flow controlling means 62 can be positionedwithin or outside of the compressor housing. For example, the flowcontrolling means 62 can be in the form of one or more variable geometrymembers that are positioned within the turbocharger. The flowcontrolling means 62 can be actuated by an engine controller or othermeans to control the amount of pressurized air that is passed out of thecompressor housing depending on the particular operating condition ofthe engine. Together, the dual compressors, variable geometry compressormembers and variable geometry turbine members operate to provideefficient turbocharger operation that meets the particular engine massflow requirements.

FIG. 9 illustrates an embodiment of a turbocharger 64 of this inventioncomprising, moving from right to left, a turbocharger housing 66comprising a turbine wheel or turbine 68 rotatably disposed therein andmounted to an end of a shaft 70 that is disposed through a centerhousing 72. A backing plate 74 is interposed between the center housing72 and a compressor housing 76. A dual compressor 78 is rotatablydisposed within the compressor housing, is mounted to an opposite end ofthe shaft 70, and is configured having a back-to-back oriented impellerfaces 80 and 82. The compressor 78, for this and all turbochargerembodiments of the invention, can be configured so that the shaft 70extends completely or only partially therethrough. Additionally, thecompressor can be configured in the form of a single part, e.g., asillustrated, or may comprise an assembly or more than one part Thecompressor housing 76 is specially configured to permit both the passageof inlet air to each compressor, and the passage of pressurized gas fromeach compressor. In this particular embodiment, the compressor housingcomprises two separate axially positioned air inlets; namely, a firstair inlet passage 84, that is positioned adjacent an end of thecompressor housing to pass inlet air in an axial direction to thecompressor face 80, and a second air inlet passage 86 that is separatefrom and positioned a distance radially away from the first air inlet84. The second air inlet 86 includes a first section 88, that extends adistance axially from an inlet opening go into the compressor housingand that is defined between an outside surface of a volute 92 and aninside wall surface of the compressor housing, and a second section 94,that extends circularly around the compressor housing and projectsradially inwardly. The second section 94 is defined by an outsidesurface of the volute 92 and an inside surface of the backing plate 74.Inlet air passing through the second section is delivered to thecompressor second face 82 via an opening 95 formed between the voluteouter wall surface and the backing plate. Pressurized air that isprovided by the compressor 78 is directed radially from each of thefaces 8o and 82 through a single passage 96 and to the volute 92.

FIG. 10 illustrates an embodiment of a turbocharger 98 of this inventioncomprising the same general turbine housing and center housingcomponents noted above for the embodiment illustrated in FIG. 9. Thisparticular embodiment includes a compressor housing that comprises thesame first and second air inlets 84 and 86 as noted above, configured todeliver air to the compressor first and second impeller faces. Thecompressor housing also includes a flow controlling means 100 disposedtherein for controlling the amount of pressurized air passed from thecompressor 78 to the volute 92.

In this embodiment, the flow controlling means 100 is provided in theform of an annular member that is movably positioned within a section ofan inner nozzle wall 102 interposed between the compressor and thevolute. The annular member 100 is positioned within a cavity 104 that issized and shaped to accommodate placement of a portion of the membertherein. The annular member 100 preferably has an outside surface 106that is configured to compliment the immediately adjacent sections ofthe inner nozzle wall to minimize any unwanted aerodynamic effects.

In this particular embodiment, the annular member 112 has amushroom-shaped profile with rounded end sections that are configured tominimize the transition of pressurized air moving from the compressor tothe volute, thereby operating to minimize unwanted aerodynamic effectswithin the compressor housing.

The annular member 100 is shown in both a unactuated and an actuatedposition (in phantom). In an unactuated position, the annular memberdoes not project towards an outer nozzle wall 110 to restrict thepassage of pressurized air from the compressor. In an actuated position,the annular member projects a defined distance towards the outer nozzlewall to restrict the passage of pressurized air produced by thecompressor second face 82 into the single passage 96. The annular membercan be actuated by mechanical, hydraulic, pneumatic or electronic meansto project in the manner described. The extent to which the annularmember projects towards the inner nozzle wall is controlled by asuitable limiting means.

Configured in this manner, the annular member 100 can be operated, byengine control unit or the like, to control the amount of pressurizedair being produced by the compressor to increase the flow range of thecompressor, thereby maximizing compressor efficiency to provide thedesired BMEP to meet the engine's mass flow requirements.

FIG. 11 illustrates an embodiment of a turbocharger 112 of thisinvention comprising the same general components noted above for theembodiment illustrated in FIG. 10. This embodiment additionally includesmeans 114 for actuating the annular member 100. The actuating means 114is in the form of a two-way valve that is configured to be moved toprovide air-flow communication between a back side of the annularmember, e.g., between the annular member and the cavity, and the volute92, or to provide an air-flow communication between a back side of theannular member and the second air passage 94. In an example embodiment,the valve 116 extends within a valve port 118 that is in air flowcommunication with the cavity 104. The valve port 118 is also in airflow communication with a the second air passage 94 and the volute 92.This can be accomplished via one or two different ports. In the exampleshown, a first port 120 connects the volute 92 to the valve port, and asecond port 122 connects the second air passage 94 valve port.

The valve 116 is configured to permit the passage of air therethroughfrom the volute to the cavity 104 when placed in one rotational positionwithin the valve port, thereby causing the annular member to move intoan actuated position, and is configured to permit the passage of airfrom the second air passage to the cavity when placed in a secondrotational position, thereby causing the annular member to move into aunactuated position. Configured in this manner, the valve can beoperated, e.g., by pneumatic, hydraulic, mechanical or electrical means,to actuate the annular member.

FIG. 12 illustrates an embodiment of a turbocharger 118 of thisinvention comprising the same general turbine housing and center housingcomponents noted above for the embodiment illustrated in FIG. 9. Thisparticular embodiment includes a compressor housing 120 having a singleor common air inlet 121 comprising concentrically arranged first andsecond air passages 122 and 124. The air inlet 121 is positioned axiallyadjacent the compressor 126. The first air passage 122 is positionedaxially inwardly a distance towards the compressor and is configured todeliver air to the compressor first face 128. The second air passage 124is positioned concentrically around the first air passage 122, andincludes first and second sections 130 and 132 that are similar indesign to those described above for the embodiment of FIG. 9 and thatare configured to deliver air to the compressor second face 134. Ifdesired, a diffuser 135 can be positioned within the second section 132to provide desired air treatment upstream of the compressor.

The compressor housing 120 further comprises a flow controlling means136 disposed therein for controlling the amount of pressurized airpassed from the compressor 126 to the volute 138. In this embodiment,the flow controlling means 136 is provided in the form of an annularmember that is movably positioned within a section of an outer nozzlewall 140 interposed between the compressor and the volute. In an exampleembodiment, the section of the outer nozzle wall incorporating theannular member can be a separate piece of the compressor housing. Theannular member 136 is positioned within a cavity 142 that is sized andshaped to accommodate placement of a base portion 144 of the membertherein. The member 136 preferably has an outside surface 145 configuredto compliment the immediately adjacent sections of the outer nozzle wall140, the volute 138, and the opposite inner nozzle wall 146 to minimizeunwanted aerodynamic effects.

In an example embodiment, the annular member 136 includes a head sectionalong one of its axial ends that is disposed outside of the cavity. Thehead includes a lip 148 that projects radially outwardly therefrom andthat is sized and shaped to forms an edge potion of the volute. The lipoperates to smoothen the transition of pressurized air moving from thecompressor to the volute, thereby operating to minimize unwantedaerodynamic effects within the compressor housing.

The annular member 136 is shown in FIG. 12 in an actuated position,projecting outwardly towards the inner nozzle wall 146 a desireddistance to restrict the passage of pressurized air from the compressor.In an example embodiment, the annular member projects a defined distancetowards the inner nozzle wall to restrict the passage of pressurized airproduced by the compressor first face 128. The annular member can beactuated by mechanical, hydraulic, pneumatic or electronic means toproject in the manner described. The extent that the annular memberprojects towards the inner nozzle wall is controlled by a suitablelimiting means. In an example embodiment, the limiting means is providedby a pair of cooperative members in the cavity and on the member. In anexample embodiment, the limiting means can be a tongue and groovemechanism. In one preferred embodiment, a tongue 150 projects within thecavity that is sized and shaped to register within a groove 152 providedin the annual member. This is but one arrangement of cooperativemembers, and it is understood than many others are within the scope andspirit of this invention.

Configured in this manner, the annular member 136 can be operated, byengine control unit or the like, to control the amount of pressurizedair being produced by the compressor to maximize improve compressorflow, thereby providing improved compressor efficiency to provide thedesired BMEP to meet the engine's mass flow requirements.

The invention embodiment illustrated in FIG. 12 includes a biasingmechanism 154 for biasing the annular member 136 in a particularposition within the cavity 142. In a preferred embodiment, the biasingmechanism 136 can be in the form of one or more springs 156 that areinterposed between the annular member 136 and the cavity 142 to causethe annular member to be biased outwardly from the cavity towards thenozzle inner wall 146. In a preferred embodiment, the annular membercomprises a number of springs that are positioned equidistantlytherearound to provide a desired biasing effect within the turbocharger.

As illustrated, when biased in this position, the annular memberoperates to impair the passage of pressurized air produced by thecompressor first face 128 into the volute 138. Once the pressure that isproduce by the compressor 126 reaches a threshold amount, it operates tooffset the force provided by the spring and causes the annular member tomove into the cavity, thereby operating to restore passage ofpressurized air from the compressor first face.

FIG. 13 illustrates an embodiment of a turbocharger 16o of thisinvention comprising the same general components noted above for theembodiment illustrated in FIG. 12. This particular embodiment comprisesan annular member 162 that is different from that disclosed andillustrated in FIG. 12 in that it does not include a head portion havinga lip that forms part of the volute. Rather, it includes a head portionwith a surface with edge portions that are shaped to blend with adjacentsurface features of the outer nozzle wall 140 and a volute lip 166.Additionally, the annular member limiting means of this embodiment isdifferent in that the annular member is configured having a pin 168 thatcooperates within a slot 170 formed in a wall portion of the cavity 142.

For purposes of reference and explanation, in FIG. 13, the annularmember 162 is shown in the actuated and unactuated position. It is to beunderstood that there is only one annular member within the compressorhousing, and that it will be actuated or unactuated position, but notboth. When placed in the actuated position 172, the engagement of thepin 168 against a wall of the slot 170 operates to limit outward travelof the annular member, thereby permitting the annular member to projecta desired distance towards the inner nozzle wall to impair the passageof pressurized air from the compressor first face 128 to the volute 138.

FIG. 14 illustrates another embodiment of a turbocharger 174 of thisinvention comprising the same general turbine housing and center housingcomponents noted for the earlier-described and illustrated embodiments.This particular embodiment comprises a compressor housing 176 comprisinga single air inlet 178 that is positioned to introduce inlet airradially relative to the compressor 180. The air inlet 178 includes apartition 180 for separating the entering air into two different airflow passages 182 and 184 that each extend in a circular manner aroundthe compressor to deliver air to respective compressor faces 186 and188. In an example embodiment, the two air flow passages are configuredas being substantially symmetric to one another. Pressurized air movesfrom the compressor first and second faces 186 and 188 to a volute 190via a common passage 192. Configured in this manner, the compressorhousing provides inlet air in substantially the same condition to bothcompressor faces to assure compressor performance.

FIG. 15 illustrates another embodiment of a turbocharger 194 of thisinvention comprising the same general turbine housing and center housingcomponents noted for the earlier-described and illustrated embodiments.This particular embodiment comprises a compressor housing 196 having oneor more air inlet (not shown) that is positioned to introduce inlet airradially relative to the compressor 198. The air inlet is directed intotwo different air flow passages 200 and 202 that each extend in acircular manner around the compressor to deliver air to respectivecompressor faces 204 and 206. The air flow passages are designed havingsubstantially the same configuration in a stacked orientation, i.e.,they are not symmetric with one another, to provide inlet air to each ofthe respective compressor faces 204 and 206 in substantially the samecondition.

The compressor housing 198 further includes an annular member 208disposed therein to control the amount of pressurized air directed fromthe compressor to the volute 210. The annular member 208 is movablydisposed within a cavity 212 of the outer nozzle wall 214. The annularmember 208 includes a surface portion 216 that is configured to providea smooth transition along the outer nozzle wall surface in an unactuatedposition. The annular member also includes a lip 218 that projectsradially inwardly adjacent the surface portion 216 that operates toblock off flow or pressurized air from the compressor first face 204when projecting from the cavity in the actuated position.

The extent that the actuating member projects from the cavity iscontrolled by a limiting means, e.g., in the form of tongue-in-groovecooperating members. In this particular embodiment, the annular memberincludes a tongue 220 projecting from a base portion, and the cavityincludes a groove 222 of determined axial length to accommodate adesired degree of axial annular member movement. The annular member canbe actuated by the same techniques discussed above.

Turbochargers of this invention comprise a compressor that is sized andconfigured to provide an improved degree of turbine matching, whencompared to conventional single compressor turbochargers, to produce thedesired BMEP to meet engine mass flow requirements. A key feature ofcompressors used with this invention is that they are sized andconfigured to provide improved turbine speed matching. Conventionalturbochargers having a single compressor force the turbine to operatetoo slowly, particularly in the low engine speed range. One solutionwould be to increase the speed of the compressor relative to theturbine. The aerodynamicist can raise the speed of the compressor byincreasing the backward curvature of the exducer blading, or increasingthe inducer area for a fixed compressor diameter. However, these choiceswill dramatically increase the aforementioned low cycle fatiguefailures.

Compressors of this invention are designed having two impellers in aback-to-back arrangement. Using the same design scaled allows thediameter of the compressor to be reduced by a factor of approximately0.7. The back-to-back compressors run at the same tip speeds as thesingle larger one, thus the stresses would be similar as would theaerodynamic performance. However, a benefit that is gained from thisconfiguration is that the absolute rotational speed of the turbochargeris increased by −40%, significantly improving the turbine match, evenpotentially allowing a reduction in the turbine diameter.

Being able to reduce the turbine diameter provides a reduced variablenozzle flow loss at engine acceleration conditions, as the smallerturbine can operate with the nozzle in a more open position at the sameflow rate. The aerodynamicist now has the option of conducting anoptimization of the turbine diameter, utilizing the exducer trim (thesquare of the ratio of exit diameter to the inlet diameter) and turbineblade exit angle against the nozzle loss. As the turbine diameter isdecreased, the nozzle opening for a given low flow condition movescloser to the optimum nozzle setting (the combination of flow vectorinto the wheel and throat of the nozzle). Also, as the turbine diameteris decreased, the maximum turbine flow must be maintained which can beaccomplished by a combination of turbine trim increase and blade wrapdecrease (reducing the exit angle of the turbine wheel).

Turbochargers of this invention, are specifically engineered to addressthe compressor flow range noted above and provide surge line improvementas the viscous wall friction of the compressor has been reduced due tothe elimination of one wall of the diffuser (when compared to twoturbochargers wheels with hub and shroud walls on each diffuser). Thehub line wall has been completely eliminated by this design.Turbochargers of this invention may further include flow controllingmeans that contribute further to surge line improvements. For example,using such flow controlling means to block the air flow through one ofthe compressors will operate to reduce the surge flow by one half.

Such flow controlling means can be operated, via suitable control means,to control the amount of pressurized air that is produced by thecompressor throughout the engine operating range to ensure that thecompressor is always operating within it flow range, thereby enabling tocompressor to efficiently meet the engine's mass flow requirements.

Turbochargers, constructed according to the principals of thisinvention, may also provide an opportunity to downsize the turbocharger,perhaps reducing the weight by a factor of two, and the rotating inertiaby a factor of eight. Turbocharger low speed response will be improvedby increased compressor and turbine efficiencies, and reduced rotatinggroup inertia. The optimum turbine performance will be moved to asignificantly lower flow range, although the turbine maximum flow willbe maintained. The compressor thrust loads will be balanced for most ofthe operating range. Heat losses to the under-hood environment will bereduced as well as the thermal inertia, significantly improving catalystlight-off time. Turbocharger packaging and manufacturing cost will bedramatically improved, particularly compared with multi-turboconfigurations. Compressor flow range will no longer be a limitingfactor to the engine low speed performance.

Having now described the invention in detail as required by the patentstatutes, those skilled in the art will recognize modifications andsubstitutions to the specific embodiments disclosed herein. Suchmodifications are within the scope and intent of the present invention.

1. A turbocharger assembly comprising: a turbine housing; a turbinewheel rotatably disposed within the turbine housing and attached to ashaft; a center housing connected to the turbine housing and carryingthe shaft; a compressor housing attached to the center housing; acompressor rotatably disposed within the compressor housing and attachedto the shaft, the compressor comprising two impellers in back-to-backorientation with one another, the compressor housing including at leastone air inlet for directing air into the compressor housing and to thecompressor impellers; and a mechanism for controlling the flow of airwithin the compressor housing.
 2. The turbocharger assembly as recitedin claim 1 wherein the compressor housing includes two separate airinlets that are in air flow communication with respective compressorimpellers, wherein the air inlets are optionally oriented to receive airaxially with respect to the compressor, and wherein the air inlets areoptionally oriented to receive air radially with respect to thecompressor.
 3. The turbocharger assembly as recited in claim 1 whereinthe compressor housing comprises a single common air inlet that is inair flow communication with respective compressor impellers, wherein theair inlet is oriented to receive air axially with respect to thecompressor, and wherein the air inlet is oriented to receive airradially with respect to the compressor.
 4. The turbocharger assembly asrecited in claim 1 wherein the mechanism for controlling comprises anannular member that is movably disposed within the compressor housingand that is positioned downstream of the compressor to control the flowof pressurized air within the compressor, wherein the annular member isoptionally movably disposed within a wall section of the compressorhousing and is optionally positioned to control the flow of pressurizedair from one of the compressor impellers when placed in an actuatedposition.
 5. A turbocharger assembly comprising: a turbine housing; aturbine wheel rotatably disposed within the turbine housing and attachedto a shaft; a center housing connected to the turbine housing andcarrying the shaft; a compressor housing attached to the center housing;a compressor rotatably disposed within the compressor housing andattached to the shaft, the compressor comprising two impellers inback-to-back orientation with one another, the compressor housingincluding at least one air inlet in air flow communication with each ofthe compressor impellers; and an annular member moveably disposed withina wall cavity of the compressor housing downstream of the compressor forcontrolling the flow of pressurized air from one of the compressorimpellers when placed in an actuated position.
 6. The turbochargerassembly as recited in claim 5 wherein the compressor housing includestwo separate air inlets that are in air flow communication withrespective compressor impellers, wherein the air inlets are optionallyarranged to receive air axially into the compressor housing with respectto the compressor, and wherein the air inlets are optionally oriented toreceive air radially with respect to the compressor.
 7. The turbochargerassembly as recited in claim 5 wherein the compressor housing comprisesa single common air inlet that is in air flow communication withrespective compressor impellers, wherein the air inlet optionallydelivers air axially into the compressor housing with respect to thecompressor, and wherein the air inlet optionally delivers air radiallyinto the compressor housing with respect to the compressor.
 8. Aturbocharger assembly comprising: a turbine housing; a turbine wheelrotatably disposed within the turbine housing and attached to a shaft; acenter housing connected to the turbine housing and carrying the shaft;a compressor housing attached to the center housing; a compressorrotatably disposed within the compressor housing and attached to theshaft, the compressor comprising two impellers in back-to-backorientation with one another, the compressor housing having a volutepositioned concentrically around the compressor and including a singleair inlet that is in air flow communication with two concentricallyoriented air flow passages, each air flow passage being in air flowcommunication with respective compressor impellers; and an annularmember moveably disposed within a wall cavity of the compressor housinginterposed between the compressor and the volute for controlling theflow of pressurized air from one of the compressor impellers when placedin an actuated position.
 9. A method for providing pressurized air forcombustion by an internal combustion engine, the method comprising:directing exhaust gas from the internal combustion engine to a turbinehousing of a turbocharger to rotate a turbine wheel rotatably disposedtherein, wherein the rotation of the turbine wheel causes a compressorto also rotate within a compressor housing; directing air into thecompressor housing and to the compressor, the compressor comprising twoback-to-back oriented impellers to produce pressurized air; andcontrolling the flow of pressurized air exiting the compressor housingfrom at least one of the impellers depending on the operating conditionsof the internal combustion engine.
 10. The method as recited in claim 9wherein the controlling comprises actuating an annular member that ismovably disposed within the compressor housing to project into an airflow path downstream of the compressor.